Furnace regulator system



g- 4 J. P. HOUCK HAL 2,292,122

FURNACE REGULATOR SYSTEM Filed Jan. 9, 1941 WITNESSES:

INVENTOR-S a James P/Vaucr and Patented Aug. 4, 1942 FURNACE REGULATORSYSTEM James P. I-Iouck and Ralph A. Geiselman, Wilkinsburg, Pa.,assignors to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a ccrporation of Pennsylvania Application January 9,1941, Serial No. 373,857

2 Claims.

This invention relates to regulator systems, and particularly toregulator systems for governing the operation of the movable electrodesin electric furnaces.

Systems for regulating the operation of a motor for raising or loweringthe electrodes of electric furnaces are well known and have beenutilized for a number of years with good results. However, with theseknown systems, it has been found that during the melting down period,the are formed between the electrode and the cold scrap melts the scrapat the bottom of the pocket formed with the result that the molten metalspreads and causes a cave-in of the unmolten metal around the electrode.When the unmolten metal contacts the electrode, a short circuitcondition is established between the electrode and the charge. Thisshort circuit condition will vary in length of time depending upon thedistance the electrode is submerged and the speed of the electrode motorin raising the electrode. It is, therefore, desirable to accelerate orobtain a speedy raising of the electrode under predetermined conditions.However, since in some cases the short circuit condition rapidly clearsitself, it is also desirable that the acceleration or the increase inthe speed of raising the electrode be delayed for a short period of timeto permit the short circuit condition to clear itself.

An object of this invention is to provide a furnace regulator systemthat shall govern the operation of the movable electrodes and effect anacceleration or increase in speed of raising the electrodes underpredetermined conditions.

Another object of this invention is to provide a furnace regulatorsystem for controlling the normal raising and lowering of the movableelectrodes and accelerate the raising of the electrodes underpredetermined conditions after a predetermined time has elapsed from theinitiation of the .predetermined conditions.

Other objects of this invention will become apparent from the followingdescription when taken I is illustrated, the furnace comprising areceptacle l2 containing a bath of material l4 and three movableelectrodes [6, I8 and 2B. The

electrodes 16, I8 and are directly connected to a three-phase supplycircuit comprising conductors 22,24 and 26, respectively.

Each of the movable electrodes is provided with a motor for raising andlowering it and a regulator for governing the operation of the motor inaccordance with the current flowing through the electrode and inaccordance with the potential across the electrode arc. Since each ofthe regulators is of like construction and operates in the same manner,it is believed to be unnecessary to illustrate and describe more thanone of them. Accordingly, only the regulator so associated with theelectrode 23 is illustrated and will be described.

In the drawing, a motor 28 comprising an armature 3!], a commutatingfield winding 32 and a shunt field winding 34 is illustrated for raisingand lowering the electrode 20. The armature is mechanically connected tothe electrode 20 in any suitable manner as by means of the shaft 35, awinding drum 3B and a flexible conductor which passes over the pulley42. The shunt field winding 34 is connected directly across supplyconductors 44 and 46, a resistor 48 being disposed to be connected inseries circuit relation with the winding 34.

A regulator 50 which normally controls the operation of the motor 28comprises two main control electromagnets 52 and 54 which are,respectively, operated in accordance with the current flowing throughthe electrode 20 and in accordance with potential across the areproduced by the electrode and two electromagnetic switches 56 and 58which, respectively, serve to connect the motor across the supplyconductors 44 and 46 in order to operate it in a clockwise and acounterclockwise direction.

The main control electromagnets 52 and 54 comprise an energizing winding60 and 62, respectively, and a core armature 64 and 66, respectively.The energizing winding 60 of electromagnet 52 is connected to thethree-phase conductor 26 by means of a current transformer 6i and itscore member 64 is pivotally connected to a contact arm 65, the coremember being provided with a dashpot 6'! for governing its speed ofoperation. The energizing winding 62 of electromagnet 54 is connectedfrom one side by conductor 69 to the three-phase conductor 26 andelectrode 20 and from the other side through conductor ll, theenergizing winding 68 of an electromagnetic switch 16 and conductor 72to the receptacle l2 containing the bath M. The core member 66 ofelectromagnet 54 is also pivotally connected to the contact arm and isprovided with a dashpot 14 for governing the speed of its operation.

As illustrated, the contact arm 65 is pivotally mounted at a pointintermediate the points of connection to the core members 64 and 66 andcarries two main contact members I6 and I6 disposed for engagement withcontact members 80 and 82, respectively, according to the position ofcontact arm 65. Springs 84 are connected to the arm 65 for maintainingit in a neutral position with the contact members I6 and I8 disengagedfrom the contact members 80 and 02 when the electromagnets 52 and 54 aredeenergized. The contact members I6 and I8 are connected to the supplyconductors 44 and 46 through a resistor 85.

The electromagnetic switch 56 comprises a Winding 86 which is connectedacross the supply conductors 44 and 46 upon engagement of contactmembers I6 and 80 and a core armature 88 which operates two contactmembers 90 and 92. The contact members 90 and 92 function upon operationof the electromagnetic switch 56 to connect the armature 36 of the motor28 across supply conductors 44 and 46 for rotating the motor 28 in aclockwise direction to lower the electrode 25 in the furnace.

The electromagnetic switch 58 comprises a winding 34 which is connectedacross the supply conductors 44 and 46 upon engagement of the contactmembers I8 and 82 and a core armature 96 which operates two contactmembers 88 and I00. The contact members 98 and I60 function uponoperation of the switch 58 to connect the armature 30 across supplyconductors 44 and 46 for rotating the motor 28 in a counterclockwisedirection to raise the electrode 25 in the furnace.

According to well known practice, a braking resistor I02 is alsoprovided in circuit with the armature 30 and the contact members 92 andI60 complete a dynamic braking circuit for the motor 26 when thewindings of the electromagnetic switches 56 and 58 are deenergized,thereby effecting a quick stopping of the motor 28. Although, not shown,suitable anti-hunting equipment may be provided in any well known mannerto prevent overtravel of the moving parts of the regulator and to give asensitive control of the operation of the motor 28.

The electromagnetic switch I6 is provided for controlling theenergization of the shunt field winding 34 of motor 28. As illustrated,the energization of the winding 68 of switch I depends only upon thepotential across the arc produced by the electrode 20. The operation ofthe switch I0 controls the operation of electromagnetic switch I04, thecontact member I96 of switch I0 being disposed when the winding 68 isdeenergized to close a circuit which extends from supply conductor 44through conductor I08, winding IIO of switch I04, conductor II2, contactmember I06 of switch I0 and conductor II4 to the supply conductor 46. Adashpot H6 is connected to the core armature of the electromagneticswitch I0 to provide a predetermined time interval or delay in theoperation of the switch I0 when the Winding 68 is deenergized to preventimmediate return of the contact member I66 to its circuit closingposition, the purpose of which will be explained more fully hereinafter.

The electromagnetic switch I64 also is provided with a core armaturewhich carries a contact member IIB which is disposed when the winding II0 is deenergized to close a circuit which extends from one end of theresistor 48 through conductor I20, contact member I I8 and conductor I22to the other end of the resistor 48 to short circuit it from the circuitof the shunt field winding 34 of motor 28.

In operation, assuming that the system is functioning to position theelectrode 20 with respect to the bath I4 for normal operation of thefurnace, a normal current flows through the electrode 20 and a normalpotential exists across the are from the electrode 20 to the bath I4.Although this potential is insuificient to so energize the winding 62 ofelectromagnet 54 to upset the balance between the pull of electromagnets52 and 54, sufiicient potential exists to so energize the winding 68 ofelectromagnetic switch I0 to actuate its contact member I06 in an upwarddirection to open the circuit of the energizing winding IIO ofelectromagnetic switch I04. Under these conditions, the contact memberII8 of the electromagnetic switch I64 short circuits the resistor 43from the circuit with the shunt field winding 34 of the motor 26.

If for any reason the current flow through the electrode 26 is loweredbelow the normal value and the potential across the are formed by theelectrode is above the normal value, the energization of the winding 60of electromagnet 52 is decreased and the energization of the winding 62of electromagnet 54 is increased to eli'ect engagement between contactmembers I6 and 80.

Upon engagement of the contact members I6 and 60, the winding 86 ofswitch 56 is energized by a circuit which extends from the supplyconductor 44 through a portion of the resistor 85, contact arm 65,contact members I6 and and the winding 86 of the switch 56 back to thesupply conductor 46. When the winding 86 is thus energized, the contactmembers 94 and 62 are actuated in an upward direction with the contactmember 96 being in the circuit closing position and the contact member92 in a circuit opening position to complete a circuit through thearmature 30 and effect rotation of the motor 28 in a clockwisedirection. The clockwise rotation of the motor 20 lowers the electrode20 in the furnace to increase the current flow through it and lower thepotential across the are formed by it. Throughout this operation theresistor 48 is short circuited from the circuit with the shunt fieldwinding 34 of the motor 28. When the electrode 20 is lowered asufiicient distance whereby the pull on the electromagnets 52 and 54 isbalanced due to an adjustment in the current flow in electrode 20 andthe potential across the arc, the balanced pull on the contact arm 65effects a separation of the contact members I6 and 80 whereby the switch56 is deenergized and the contact members 90 and 92 are returned totheir circuit opening and circuit closing positions, respectively, and adynamic braking circuit through the braking resistor I02 is establishedfor the motor 28 to effect a quick stopping of the motor.

Assuming that the electrode 20 is in position with respect to the chargeof the furnace to effect a melting of the charge, if due to the meltinga portion of the cold charge should cave-in and come in direct contactwith the electrode 20, a direct short circuit of the winding 62 ofelectromagnet 54 is established to immediately effect a separation ofthe contact members I6 and 80 and prevent further lowering of theelectrode 20 in the bath. Under such short circuit conditions thewinding 60 of electromagnet 52 is so energized as to actuate the contactarm 65 to the position where contact member I8 engages contact member 82to close a circuit which extends from supply conductor 64 through a partof the resistor 85, contact arm 65, contact members I8 and 82 and thewinding 54 of switch 58 to the supply conductor 45. When the winding 94of switch 58 is thus energized, contact members 98 and I of switch 53are actuated in an upward direction to their circuit closing and circuitopening positions, respectively, whereby a circuit is completed throughthe armature 30 to efiect rotation of the motor 28 in a counterclockwisedirection to raise the electrode 20 from the bath.

At the same time that winding 62 of electromagnet 54 is deenergized, thewinding E8 of the electromagnetic switch I0 is also deenergized.However, the contact member I06 of the switch I0 is not immediatelyreturned to its circuit closing position, since the dashpot IIGassociated with its core member prevents the return of the contactmember I06 to its circuit closing position for a predetermined intervalof time. This predetermined interval of time is usually so adjusted thatfor momentary short circuits the contact member I06 is retained in itscircuit opening position.

However, since the speed of raising the electrode 20 under normaloperating conditions is usually set at some constant speed, if thecharge has so caved in about the electrode 20 as to effeet a shortcircuit of long duration, in order to accelerate or increase the speedof raising the electrode 20, after a predetermined time delay, thedashpot IIB functions to permit the contact member I06 to close thecircuit extending from supply conductor 44 through conductor I08,winding III] of switch I04, conductor IIZ, contact member I06 of switchI0 and the conductor I I4 to the supply conductor 46. When the windingIIO of switch I04 is thus energized, the contact member H8 is actuatedto its circuit opening position to remove the short circuit from aroundthe resistor 48, thereby inserting the resistor 48 in series circuitwith the shunt field winding 34 to thereby decrease its energization andpermit the motor 28 to gain speed due to the weakened field. The changein the energization of the shunt field winding 34 of the motor 28effectively accelerates or increases the speed of the raising of theelectrode 20 from the bath I4 of the charge of material. Removal of theshort circuit condition between the electrode 20 and the bath I4, ofcourse, permits the pull of electromagnets 52 and 54 to again becomebalanced and the winding 68 of switch I0 to again become energized todeenergize the winding I I0 of switch I04 and again establish the shortcircuit about the resistor 48 to place the system in condition fornormal raising and lowering operation of the electrode 20.

Modifications in the system and arrangement and location of parts may bemade within the spirit and scope of this invention, and suchmodifications are intended to be covered by the appended claims.

We claim as our invention:

1. In an arc furnace-regulator system, a movable electrode, a motorprovided with a shunt field winding disposed for raising and loweringthe electrode, a resistor disposed to be connected in series circuitrelation with the shunt field winding of the motor, a regulatorcomprising a current electromagnet energized in accordance with thecurrent flowing through the electrode and a potential electromagnetenergized in accordance With the potential across the electrode are foroperating the motor to maintain the are produced by the electrodesubstantially constant, means in series circuit relation with thepotential electromagnet and dependent only on the potential operableunder predetermined conditions to connect the resistor in series circuitwith the shunt field winding to acelerate the operation of the motor andeffect an increase in the speed of raising the electrode, and meanscomprising a time delay device for preventing said means in seriescircuit with the potential electromagnet from connecting the resistor inseries with the shunt field winding for a predetermined period of timeto prevent premature acceleration of the operation of the motor.

2. In an arc furnace-regulator system, a movable electrode, a motorprovided with a shunt field winding disposed for raising and loweringthe electrode, a resistor disposed to be connected in series circuitrelation with the shunt field winding of the motor, a regulatorcomprising a current electromagnet energized in accordance with thecurrent flowing through the electrode and a potential electromagnetenergized in accordance with the potential across the electrode are foroperating the motor to maintain the are produced by the electrodesubstantially constant, an electromagnetic means disposed for normallyshort circuiting the resistor from the shunt field winding, means inseries circuit relation with the potential electromagnet and dependentonly on the potential operable under predetermined conditions toenergize the electromagnetic means and actuate it to connect theresistor in circuit with the shunt field winding to accelerate theoperation of the motor and effect an increase in the speed of raisingthe electrode, and means comprising a time delay device for preventingthe energization and actuation of the electromagnetic means for apredetermined period of time to prevent premature acceleration of theoperation of the motor.

JAMES P. HOUCK. RALPH A. GEISELMAN.

